Intravesical Onabotulinum Toxin A (Botox A) injections is a commonly used minimally invasive surgical procedure for treatment of overactive bladder (OAB) symptoms refractory to first and second-line therapies. Prospective randomized control studies show success rates around 60% in symptomatic OAB patients. We present the largest reported single-centre  audit of long-term outcomes for Botox A injections for refractory non-neurogenic OAB. We have assessed whether patient outcomes can be predicted by pre-operative urodynamic findings.

A retrospective review of consecutive 418 patients (age range 22-94 years, median 61 years, 128 (30%) men) having intravesical Botox A injections for refractory non-neurogenic OAB symptoms under the care of 4 consultant surgeons between 2006 and 2018 was conducted. The outcome of treatment was categorized using a 5 point Patient Global Impression of Improvement (PGI-I) scale at the last follow up appointment or when contacted by telephone if last review was over 6 months ago. Successful outcomes were defined as PGI-I scores of 1 and 2 (good effect and partially good effect). Patient outcomes were correlated with the pre-operative urodynamic findings, including presence of urge urinary incontinence (OAB-wet), idiopathic detrusor overactivity (IDO), peak DO pressure, bladder capacity at onset of first DO, and evidence of bladder outlet obstruction (BOO). Duration of voiding detrusor contraction was noted in urodynamic studies with a valid voiding phase; however, studies with no evidence of voluntary detrusor contraction, where void was initiated on top of  underlying DO, or where the intra-vesical catheter was expelled part-way through the void were excluded.  Statistical analysis was done by Students T-Test and Chi Square Test and significance was determined at P < 0.05.

Pre-operative urodynamic results were available for review on 309 (74%) patients; 214 women (age range 22-90 years, median 59 years) and 95 men (age range 27-94 years, median 69 years) and were a mixture of conventional cystometrograms (CMG), video-cystometrograms (VCMG) and ambulatory cystometrograms. Urodynamically proven IDO was demonstrated in 215 cases (69%) prior to Botox-A injections. The outcomes are listed in Table 1.

Intravesical Botox A was significantly more successful in women with urodynamically proven idiopathic detrusor overactivity (75%) comparing with men (60%) and women with OAB in absence of detrusor overactivity (62%). Successful outcomes were significantly associated with increased duration of voiding detrusor contractions but not with any other urodynamic parameters.

The gender difference is in agreement with previously published results [1,2], however our results also highlight statistically significant difference in outcomes for women with and without IDO. This is contrary to the only reported cohort study which found no difference in outcomes after intravesical Botox-A injections in patients with and without detrusor overactivity [3].

Walker et al. (2019) Onabotulinum toxin A Injections in Men With Refractory Idiopathic Detrusor Overactivity. Urology. 2019 Jan;123:242-246. doi: 10.1016/j.urology.2018.09.016
Hsiao et al. (2016) Factors associated with therapeutic effi¬cacy of intravesical onabotulinumtoxinA injection for overactive bladder syndrome. PLoS One. 2016;11(1):e0147137
Jackson et al. (2012) Intravesical botulinum toxin for overactive bladder syndrome without detrusor overactivity. British Journal of Medical and Surgical Urology 2012; 5(4): 169-173 doi: 10.1016/j.bjmsu.2011.10.003